JP2007168220A - Inkjet head and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device capable of preventing air bubbles from staying near a filter in an ink channel. <P>SOLUTION: An inkjet head includes a plurality of grooves made to communicate with nozzle openings, an ink chamber for supplying ink to each of the grooves, an ink reservoir for making an ink storage means storing the ink and the ink chamber communicate with each other, and the filter for allowing the ink to pass through into the ink reservoir. It is composed so as to make a part of the filter, that is, the end part on the filter located far from an ink inlet of the ink reservoir or the whole of the filter, water-repellent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet head and an ink jet recording apparatus applied to, for example, a printer and a fax machine.

  2. Description of the Related Art Conventionally, an ink jet recording apparatus that records characters and images on a recording medium using an ink jet head that discharges ink from a plurality of nozzles is known. In such an ink jet recording apparatus, an ink jet head that faces a recording medium is fixed to a head holder, and the head holder is mounted on a carriage and scanned in a direction orthogonal to the conveyance direction of the recording medium.

  As such an ink-jet head, for example, a groove-shaped chamber communicating with a nozzle opening is provided in a piezoelectric ceramic plate, electrodes are formed on both side walls of the chamber, and an electric field is applied to the side walls. A head chip that changes the volume and ejects ink droplets from nozzle openings has been proposed.

  In the ink jet head configured as described above, the ink between the ink storage portion and the chamber when the ink jet head is assembled in an ink jet recording apparatus after manufacture or when the ink jet head is replaced or the ink storage portion is replaced. Air may enter the flow path and the chamber. The air that has entered in this way may cause ink supply failure or ink ejection failure to the chamber. For this reason, by sucking the chamber and the ink flow path from the nozzle opening, the chamber and the ink flow path are filled with ink, and bubbles in the chamber and the ink flow path are removed.

  However, the ink flow path is provided with an ink reservoir that communicates the ink reservoir and the chamber, and even if ink is sucked from the nozzle opening, the ink flow is not substantially interfered with the ink flow. Bubbles accumulate in the area. In particular, when a filter is provided inside the inkjet head, bubbles tend to accumulate on the ink storage part side (upstream side in terms of ink flow) of the filter. This bubble changes the volume of the ink reservoir, and the ink supply amount differs between the central area and the both end areas of the parallel chambers. There is a problem that occurs.

In order to solve such a problem, as disclosed in Japanese Patent Application Laid-Open No. 2002-337352, a bubble discharge path for discharging bubbles to the outside is provided in an ink transfer section that transfers ink from an ink tank to an inkjet head. An ink tank, an ink jet head, an ink jet recording unit, and a printer having suction means provided at the other end of the discharge path have been proposed. In particular, in a filter unit installed in an ink flow path in which a meniscus is formed by ink and bubbles are difficult to be discharged, as shown in Japanese Patent Application Laid-Open No. 2002-52730, ink is allowed to flow slowly from below the filter. As disclosed in Japanese Laid-Open Patent Publication No. 2002-361892, it is considered to discharge bubbles in the vicinity of the filter, particularly on the upstream side of the filter, by means of finely branching the ink flow path immediately before the filter.
JP 2002-337352 A JP 2002-52730 A Japanese Patent Laid-Open No. 2002-361892

However, the conventional inkjet head that provides a bubble discharge path and sucks bubbles by the suction means requires a suction device such as a suction pump as the suction means, which complicates the inkjet head and increases the cost. There is.
In addition, the method of introducing ink from the bottom or the method of branching the flow channel structurally complicates the ink flow channel, and causes problems in terms of manufacturing and assembly costs and component sizes.

In order to solve the above problems, the present invention includes a plurality of grooves communicating with the nozzle openings,
The ink jet head includes an ink chamber that supplies ink to each of the grooves, an ink reservoir that supplies ink to the ink chamber, and a filter that is provided in the ink reservoir and has a water-repellent portion at least partially.

  By adopting the above structure, bubbles staying on the upstream side of the filter can be effectively discharged. In addition, since there is no need to make major changes to the flow path structure, it is possible to easily shift from the current specification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of an inkjet head in the present embodiment. FIG. 2 is a cross-sectional view taken along the line AA showing the main part of the inkjet head, and FIG. 3 is a cross-sectional view taken along the line BB showing the main part of the inkjet head.

  FIG. 8 is a schematic perspective view of the inkjet head chip used in the embodiment of the present invention. As shown in FIG. 8, a plurality of grooves 102 are arranged in parallel on the piezoelectric ceramic plate 101 provided in the inkjet head chip 6, and each groove 102 is separated by a side wall 103. One end in the longitudinal direction of each groove 102 extends to one end face of the piezoelectric ceramic plate 101, and the other end does not extend to the other end face, and the depth gradually decreases. In addition, an electrode 105 for applying a driving electric field is formed on the opening side surface of both side walls 103 in each groove 102 over the longitudinal direction.

  A cover plate 107 is bonded to the opening side of the groove 102 of the piezoelectric ceramic plate 101 with an adhesive. The cover plate 107 includes a common ink chamber 111 serving as a recess communicating with the shallower other end of each groove 102, and an ink supply port 112 penetrating from the bottom of the common ink chamber 111 in a direction opposite to the groove 102. Have

  In addition, a nozzle plate 115 is joined to an end face where the groove 102 of the joined body of the piezoelectric ceramic plate 101 and the cover plate 107 is opened, and a nozzle opening is provided at a position facing each groove 102 of the nozzle plate 115. 7 is formed.

  The wiring substrate 20 is fixed to the surface of the piezoelectric ceramic plate 101 opposite to the nozzle plate 115 and opposite to the cover plate 107. A wiring pattern 122 connected to each electrode 105 by bonding wires 121 and the like is formed on the wiring board 20, and a driving voltage can be applied to the electrode 105 through the wiring pattern 122.

  In the ink jet head chip configured as described above, when each groove 102 is filled with ink from the ink supply port 112 and a predetermined driving electric field is applied to the side walls 103 on both sides of the predetermined groove 102 via the electrodes 105, The side wall 103 is deformed to change the volume in the predetermined groove 102, whereby the ink in the groove 102 is ejected from the nozzle opening 7.

  As shown in FIGS. 1 and 2, the inkjet head 1 of the present embodiment drives the head chip 6, the ink flow path 2 provided so as to communicate with the ink supply port 112 of the head chip 6, and the head chip 6. A wiring board 20 on which a drive circuit for mounting and the like is mounted, and a pressure relaxation mechanism 22 that relieves pressure changes in the head chip 6. These members are fixed to the base plate 21, respectively.

  As shown in FIGS. 2 and 3, an ink reservoir 3 is formed in the ink flow path 2, and a filter 4 is installed in the ink reservoir 3. The filter 4 has a filter opening area of about 5 to 15 micrometers and prevents dust and the like from entering the head chip 6. Various types of filters 4 such as metal and resin can be used, but metal filters are often used because of durability, cost, and mass productivity in the manufacturing process. Further, on the filter 4, there is a water-repellent portion 10 which is water-repellent at an end portion far from the ink inflow portion 5 and in contact with the side wall of the ink flow path 2 or the ink reservoir 3. . As a treatment method for imparting water repellency, a vacuum deposition method in which fluorine molecules are deposited in vacuum or a coating agent can be applied, but it is necessary to have a film thickness that does not hinder the opening of the filter 4. . The water-repellent portion 10 is sufficient if it has a range of about 1 mm in diameter, and may be wider than that. In FIG. 3, since the ink inflow portion 5 is near the center of the filter 4, the water-repellent portions 10 exist at both ends of the filter 4, but when the ink inflow portion 5 is near one end of the filter 4. The water repellent portion 10 is located at the end opposite to the ink inflow portion 5.

  Here, ink filling using this embodiment will be described. When ink is filled, ink is supplied from the ink inflow portion 5 to the ink reservoir 3, and a certain amount of dust and bubbles are removed by the filter 4, so that ink is supplied into the head chip 6. As a method for filling ink, there are a method in which a cap is pressed against the nozzle opening 7 side to apply a negative pressure and the ink is sucked, and a method in which ink is pressurized and filled from the ink inflow portion side.

  In any of the filling methods, the present embodiment satisfies the function, but the state in the case where ink is filled by suction will be described below. When the ink jet head 1 is not used, the inside of the ink flow path 2 is dry, and the bubbles 9 are difficult to collect in the ink reservoir 3. However, in actuality, the filter 4 is often wet with the delivery liquid or ink when the inkjet head 1 is filled with the delivery liquid or when the ink is once removed and refilled. As shown in FIG. 4, when the filter 4 does not have the water repellent portion 10, an ink meniscus 8 is formed on the filter 4 due to the surface tension of the ink. When ink filling is started in a state where the ink meniscus 8 is formed, the ink flowing from the ink inflow portion 5 comes into contact with the filter 4. At this time, a resistance force for the ink to pass through the filter 4 and a force for the bubbles 9 on the upstream side of the filter 4 to break the meniscus 8 formed in the filter 4 are generated. When the contact area of the ink with respect to the filter 4 is narrow, the flow area becomes narrow with respect to the same flow rate, so that the ink passage resistance increases. Then, the ink passage resistance becomes larger than the force that breaks the meniscus 8, so that the bubbles 9 on the upstream side of the filter 4 break through the meniscus 8 of the filter 4 and pass through. As the flow area of the filter 4 increases as the bubbles 9 on the upstream side of the filter 4 become smaller, the ink passage resistance decreases and becomes smaller than the force that breaks the meniscus 8. Then, the bubbles 9 cannot pass through the filter 4 and stay on the upstream side of the filter 4. This bubble 9 causes an ink supply failure and an ink ejection failure.

  In the present embodiment, as shown in FIG. 5, the water repellent portion 10 is present on the filter 4, and thus no ink meniscus 8 is formed on the water repellent portion 10. When filling is started in this state, the ink flowing from the ink inflow portion 5 comes into contact with the filter 4. At this time, although the resistance force that the ink passes through the filter 4 works, the meniscus 8 is not formed at the end of the filter 4, so that the bubbles 9 can pass through the filter 4 without the resistance force acting. For this reason, the ink 9 passes through the filter 4 after all of the bubbles 9 have passed, so that the bubbles 9 do not stay on the upstream side of the filter 4. Therefore, the problem caused by the bubbles 9 can be solved.

  Further, even when the entire surface of the filter 4 has water repellency as shown in FIG. 6, since the bubbles 9 do not stay on the upstream side of the filter 4 during filling, the same effect can be obtained.

  Here, a serial type ink jet recording apparatus equipped with the above-described ink jet head 1 will be described. FIG. 7 is a configuration diagram schematically showing a basic configuration of the ink jet recording apparatus. In FIG. 7, a carriage 30 is mounted with the inkjet head 1, and is supported on a recording medium (not shown) disposed below the inkjet head 1 so as to be able to reciprocate in a main scanning direction perpendicular to the conveyance direction of the recording medium. .

  Further, a service station for cleaning the inkjet head 1 and the like is provided outside the non-printing area in the main scanning direction, and a capping portion 31 for sealing the nozzle formation surface of the inkjet head 1 is disposed in this service station. Has been. A negative pressure can be applied to the capping unit 31 by a suction pump 32, and an air release valve is provided so that the negative pressure state of the capping unit 31 can be opened. By configuring in this way, it is possible to remove dust accumulated in the inkjet head 1 (cleaning operation) and to perform an initial ink filling operation into the apparatus.

  The ink storage section 40 serving as an ink supply source has a structure that can be mounted in an ink storage section storage section 50 provided at a predetermined position in the apparatus. The ink reservoir 40 includes an air shielding container 41 that can store ink sufficiently deaerated during the ink injection process. In this example, the air shielding container 41 is a gusset made of a flexible material. This is a bag-type ink pack of a type, and a sufficient quality gas barrier property is secured by providing an aluminum foil layer on one layer of a flexible material. An ink supply path 33 is provided so as to supply ink from the ink reservoir 40 to the pressure relaxation mechanism 22 of the inkjet head 1.

  Although the configuration of this figure has described the configuration including one recording head 1 corresponding to one printing color in the serial type ink jet recording apparatus, the head-fixed line type printer or the flatbed type for moving the recording object. The same effect can be obtained also in the printer, and other embodiments are not excluded as long as they meet the gist of the present embodiment.

The figure which shows typically the basic composition which concerns on the inkjet head which concerns on embodiment of this invention. Typical sectional drawing from the side which shows the principal part of the inkjet head of the present invention Typical sectional drawing from the front which shows the principal part of the inkjet head of the present invention The figure which showed the mode of the ink at the time of filling in the conventional ink jet head typically The figure which showed typically the mode of the ink at the time of filling in the inkjet head of Example 1 of this invention. The figure which showed typically the mode of the ink at the time of filling in the inkjet head of Example 2 of this invention. 1 schematically shows a basic configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 8 is a perspective view of the inkjet head chip used in the embodiment of the present invention.

Explanation of symbols

1 Inkjet head (recording means)
2 Ink flow path 3 Ink reservoir 4 Filter 5 Ink inflow part 8 Meniscus 9 Bubble 10 Water repellent part

Claims (4)

A plurality of grooves communicating with the nozzle openings;
An ink chamber for supplying ink to each of the grooves;
An ink reservoir for supplying ink to the ink chamber;
A filter provided in the ink reservoir and having a water repellent portion at least in part;
Inkjet head including.   2. The ink jet head according to claim 1, wherein the water repellent portion is provided in a part of a filter separated from an ink inflow portion into the ink reservoir.   2. The ink jet head according to claim 1, wherein the water repellent portion is provided over the entire surface of the filter.   2. An ink jet recording apparatus comprising: the ink jet head according to claim 1; and an ink reservoir that stores ink to be supplied to the ink jet head.

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